Implement the roff(7) .shift and .return requests,

for example used by groff_hdtbl(7) and groff_mom(7).

Also correctly interpolate arguments during nested macro execution
even after .shift and .return, implemented using a stack of argument
arrays.

Note that only read.c, but not roff.c can detect the end of a macro
execution, and the existence of .shift implies that arguments cannot
be interpolated up front, so unfortunately, this includes a partial
revert of roff.c rev. 1.337, moving argument interpolation back into
the function roff_res().

1 files changed, 7 insertions, 4 deletions

diff --git a/roff.7 b/roff.7
index 2fc7638e..edd931fe 100644
--- a/roff.7
+++ b/roff.7
@@ -1472,8 +1472,8 @@ Currently ignored.
 Set the maximum stack depth for recursive macros.
 This is a Heirloom extension and currently ignored.
 .It Ic \&return Op Ar twice
-Exit a macro and return to the caller.
-Currently unsupported.
+Exit the presently executed macro and return to the caller.
+The argument is currently ignored.
 .It Ic \&rfschar Ar font glyph ...
 Remove font-specific fallback glyph definitions.
 Currently unsupported.
@@ -1522,8 +1522,11 @@ This is a Heirloom extension and currently ignored.
 Change the soft hyphen character.
 Currently ignored.
 .It Ic \&shift Op Ar number
-Shift macro arguments.
-Currently unsupported.
+Shift macro arguments
+.Ar number
+times, by default once: \e\e$i becomes what \e\e$i+number was.
+Also decrement \en(.$ by
+.Ar number .
 .It Ic \&sizes Ar size ...
 Define permissible point sizes.
 This is a groff extension and currently ignored.